This invention relates to electric pumps and more particularly to centrifugal pumps where the impeller is integrally formed with the rotor of an electrical motor.
Spherical centrifugal pumps commonly have an impeller secured to the rotor of the driving electrical motor. Since the rotor is immersed in the fluid being pumped, it is customarily balanced on a single-ball bearing. The stator located outside the fluid-carrying chamber feature a winding arranged in an axial direction and wound around the piece of a complicated stator frame. These motors suffer from considerable EDDY current and ohmic losses. When the pump is not powered, the rotor is no longer balanced by magnetic and gyroscopic forces and may tilt into an eccentric position. When the pump is started, considerable wear is caused upon the bearing before the stator assumes its correct axial alignment. The motors in such pump tend to have a relatively extended axial length.
The principal and secondary objects of this invention are to provide an electrically powered compact centrifugal pump where the rotor mounting the impeller is immersed in the fluid being pumped and is balanced on a single-ball bearing and kept firmly on that bearing in proper axial alignment in the absence of any electrical supply to the motor featuring a substantially reduced axial length compared to pump motors of prior art.
These and other valuable objects are achieved by using a permanently-magnetized rotor having a first upper surface mounting the impeller and a lower, axially opposite second surface of a smaller diameter. The peripheral wall of the rotor defines a spherical sector. The rotor is balanced on a spherical bearing including a ball mounted at the tip of a pillar or post extending from the pump housing into an axial cavity in the second smaller-diameter end. An annular stator has a yoke made of soft magnetic material and has a bowl-shaped inner surface that mirrors the outer face of the rotor. A sherical septum extending through the air gap between the rotor and the stator forms a barrier preventing the fluid being pumped from being in contact with the stator. A spherical winding comprising a plurality of segments arranged in a circular configuration is secured against the inner face of the yoke. The magnetic force generated by the rotor urges the rotor firmly against its bearing in a uniform and balanced manner in the absence of any power being supplied to the pump motor.